This invention relates to a carburetor and more particularly to an improved slow and idle fuel supply system for charging forming devices.
As is well known, the carburetor associated with internal combustion engines includes an idle circuit for supplying fuel to the induction system when the throttle valve is in its idle position. Such idle discharges normally include an idle port that opens into the intake passage on the downstream side of the throttle valve when the throttle valve is in its idle position. In addition, it is common to provide the carburetor with transition ports that are disposed in proximity to the idle position of the throttle valve but on the upstream side of it. These transition ports provide air for the idle circuit when the idle port is discharging and also discharge a fuel/air mixture when the throttle valve is opened slightly beyond its idle position. In order to provide good running at idle and low speeds, it is desirable that the idle and transition ports discharge a relatively rich fuel mixture. However, when the engine is operating beyond its low speed conditions, this additional fuel discharge from the idle and transition ports can result in poor fuel economy and also in high degrees of exhaust gas emissions.
It is, therefore, an object of this invention to provide an improved idle and low speed fuel discharge circuit for a carburetor.
It is a further object of this invention to provide a charge forming device for internal combustion engines that provides good running at idle and off idle while at the same time insuring good economy when operating in the higher speed and load ranges.
It is yet a further object of this invention to provide an enrichment device for a change forming device that provides enrichment at low and idle speeds and yet provides no enrichment when running at higher loads.